I just found this on this post and thought it was really smart -- a subtle analysis of the often-subtle difference between sympathizing and derailing.
It's quite obvious that "being mistaken for the help" happens more often to POC than white folk.
It's also clear that a lot of times when people jump in with a "But that happens to me too!" they're often trying to say "Therefore what happens to you isn't really about race and you're just deluded". And that's obviously bad.
OTOH, "That happens to me too!" is a pretty normal method of expression and bonding between people... if one person describes something happening to them, others will naturally chime in with similar experiences, not because they want to make the situation All About Them, but because they want to both give and feel the happy sharing you-are-not-alone feeling. Sympathy.
Really, it's the "but" that's key. The "but" is denying the first experience's validity. The other is just potentially a bit clueless.